1. Field of the Invention
The present invention relates generally to power equipment for cutting concrete, and more specifically to a series of collar embodiments for installing on each side or face of the blade of a concrete saw. The present collars serve to stiffen the relatively thin circular blade, thus reducing vibration and lateral flexing of the blade to provide a more true cut and reduce chipping and spalling of the edges of the cut. The present collars enable saws constructed for cutting cured concrete to be utilized for cutting “green” concrete, i.e., concrete which has not completely cured, thus obviating need for an expensive specialty saw for such work.
2. Description of the Related Art
It is universal practice when pouring relatively large slabs of concrete, to provide expansion joints uniformly across the slab to allow the slab to expand and contract laterally without breaking up in an irregular pattern. These expansion joints may be formed by installing separations across the slab form when the concrete is poured, but are generally cut partially through the slab using a circular saw after the concrete has at least partially cured. These regular cuts form stress risers in the slab, and the concrete later cracks in a controlled manner along these expansion joint cuts.
These expansion joint cuts may be made at any time after the concrete sets up sufficiently to maintain its shape. Most concrete contractors prefer to cut the expansion joints when the concrete is still “green,” i.e., just after it has set up sufficiently to hold its shape, but before it has fully cured to maximum hardness. This enables the contractor to form the expansion joints very soon after pouring the slab, generally only a matter of a few hours. This often allows the contractor to make the cuts while still at the work site, rather than requiring a second trip to the site at a later date after the concrete has cured. It is clearly much more efficient to cut the expansion joints as soon as possible after pouring the concrete, rather than returning later for such work.
However, cutting such “green” concrete poses problems, perhaps the most critical of which is the lack of support for equipment and workers provided by the relatively soft concrete. Also, “green” concrete in its relatively soft state, is prone to breaking up and spalling along the edges of the freshly sawed cut. Accordingly, specialized saws have been developed for cutting very freshly poured concrete, to overcome the above problems. These “green concrete” or “early entry” saws differ from more conventional saws in that they include a relatively broad, flat support plate with a relatively narrow slot through which the blade disk extends. The span of the plate distributes the weight of the saw over the slab, while the narrow slot results in the plate extending essentially to the edge of the cut and bearing upon the concrete immediately adjacent the cut, to hold it in place while cutting.
The specialized “green concrete” or “early entry” saws are relatively expensive compared to other types of circular saws used for cutting fully cured concrete, and are often relatively limited only for use with “green” concrete. Yet, concrete contractors often find it to be more cost efficient to purchase one or more such expensive saws for “green concrete” work so they can form the expansion joint cuts in a freshly poured slab when it is partially cured, just a few hours after pouring, rather than having to return to the job site a day or more later to make the cuts. This is particularly true of larger concrete contracting companies, which have the finances to purchase the relatively costly “green concrete” saws. Smaller companies often cannot afford to purchase such a specialized concrete saw, and are forced to make an extra trip to the site to saw the expansion joint cuts with a saw for use in hard concrete, after the concrete has cured completely.
The reason that conventional saws used for cutting cured, hard concrete are generally unsuccessful at cutting “green” concrete, is that the circular saw blade extends from its attachment to the shaft as a relatively thin, unsupported disc for most of its diameter. Slight imbalances and/or lack of trueness in the blade attachment, can result in the blade having some slight motion out of the ideal plane of rotation. Furthermore, the relatively thin blade can vibrate laterally due to vibration from the drive train of the saw and/or contacting irregularities in the concrete. The relatively soft, “green” concrete breaks up more easily along the edges of the cut, due to such lateral vibration of the blade.
The present invention provides a solution to the above problem by a series of collar embodiments which are installed in pairs to the blade of a concrete saw, with the blade being sandwiched tightly between the two collars. The collars have diameters on the order of only two inches or so less than the diameter of the blade to which they are attached, and thus limit the unsupported portion of the blade to a relatively narrow toroidal area between the clamps and the blade periphery. This does not limit the utility of the tool, as the typical expansion joint cut is only on the order of about one and one half inches deep. Thus, the two inch peripheral area of the blade when used with the present collars, provides sufficient cutting depth for normal expansion joint cuts, and in fact can also serve as a depth stop to limit the depth of the cut to no more than the difference between the radius of the blade and the radius of the collar.
The present collars comprise several embodiments, differing primarily in their diameters for use with different diameter saw blades. In each case, however, the central portion of each collar has a slight relief area or depression, with a raised clamping area therearound. Securing the collars to each side of the saw blade, results in the central areas of the two collars being forced toward the opposite faces of the blades, with the raised clamping areas of the collars applying a substantial clamping force to the blade therebetween to preclude lateral movement of the blade.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,236,356 issued on Dec. 2, 1980 to John D. Ward, titled “Cutting Saw And Concrete Groover,” describes a small, hand operated saw which may include a series of ganged blades for cutting a series of parallel grooves in concrete. The Ward saw is adapted particularly for use in narrow, confined areas, as in cutting traction grooves in concrete step treads. Ward does not provide any form of clamping collars which subtend a substantial portion of the area of the circular blades and which substantially prevent lateral flexing and vibration of the blades, as provided by the present stabilizing collar invention.
U.S. Pat. No. 4,769,201 issued on Sep. 6, 1988 to Edward Chiuminatta et al., titled “Method Of Cutting Grooves In Concrete With A Soft Concrete Saw,” describes a device embodying the basic concept or principle behind a concrete saw adapted for use in cutting “green,” or partially cured, concrete. The Chiuminatta et al. saw employs a platform with a skid plate extending therebelow, with the platform and skid plate each having a very narrow slot therein through which the circular blade extends. This greatly reduces the chipping or spalling of the edges of the saw cut, as the skid plate bears downwardly along the very edges of the cut and tends to preclude unstable movement of the material due to blade vibration. However, Chiuminatta et al. do not address the basic cause of such breakup and spalling in the first place, i.e., lateral movement and vibration of the blade out of the ideal plane of rotation. The present stabilizing collars address this problem, and substantially preclude blade vibration.
U.S. Pat. No. 5,167,215 issued on Dec. 1, 1992 to Edward M. Harding, Jr., titled “Dust Removal Apparatus For A Concrete Saw,” describes a conventional concrete saw with a dust removal hose and vacuum source for drawing dust laden air from the vicinity of the saw blade. The Harding, Jr. machine with its dust capturing means is clearly directed to cutting fully cured, dry concrete, which is not so prone to breaking up along the edges of the saw cut as is “green” concrete. Accordingly, Harding, Jr. does not provide any means of preventing blade vibration or other means of preventing the edges of the saw cut from chipping or spalling.
U.S. Pat. No. 5,381,780 issued on Jan. 17, 1995 to Darrell A. Yelton et al., titled “Green And Cured Concrete,” describes a concrete saw having a cutting guide which bears against the underlying concrete surface to distribute the load of the machine thereon. The Yelton et al. saw is thus similar to the saw of the Chiuminatta et al. '201 U.S. Patent discussed further above, but provides different handle and other structure. In any event, Yelton et al. do not address the issue of lateral vibration of the blade and its damaging effect on cuts made “green” concrete. The blade flanges which clamp the circular blade onto the shaft are relatively small in comparison to the diameter of the blade, as is clearly shown in FIGS. 1 and 2 of the Yelton et al. drawings. No collars having diameters approaching the diameter of the circular blade and clamping the blade therebetween to preclude lateral flexing of the blade, are disclosed by Yelton et al.
U.S. Pat. No. 5,570,677 issued on Nov. 5, 1996 to Edward R. Chiuminatta et al., titled “Method And Apparatus For Cutting Wet Concrete,” describes a saw having a spring loaded bearing plate beneath the saw blade. The plate includes a narrow slot therein through which the blade extends, as in the saw of the Chiuminatta et al. '201 U.S. Patent discussed further above. The Chiuminatta et al. '677 U.S. Patent does not provide any relatively large flanges or collars to secure the blade in place. Chiuminatta et al. clearly do not anticipate the need for such in order to reduce blade vibration, as they respond to the problem of imperfect cuts in “green” concrete in a different way, i.e., by providing a bearing plate with a very narrow slot therein for the blade to pass therethrough.
U.S. Pat. No. 5,575,271 issued on Nov. 19, 1996 to Edward R. Chiuminatta et al., titled “Apparatus For Cutting Wet Concrete,” describes a saw essentially the same as the saw of the '677 Chiuminatta et al. U.S. Patent discussed immediately above. The '677 and '271 Chiuminatta et al. U.S. Patents are continuations of the same parent patents to the same inventors, and while they each claim somewhat different matter, the devices disclosed in each patent are essentially the same. Accordingly, the discussion of the differences between the machine of the Chiuminatta et al. '677 U.S. Patent and the present invention, is seen to apply here as well.
U.S. Pat. No. 6,666,939 issued on Sep. 16, 1997 to Edward Chiuminatta et al., titled “Soft Concrete Saw,” describes essentially the same device as that described in the '201 U.S. Patent to the same patentees and described further above. The '201 U.S. Patent is the parent document for the '939 U.S. Patent, with several intervening generations of issued patents and abandoned applications between the two. While the claims differ between the '939 and '201 Patents, the structures disclosed are essentially the same, and it is felt that the discussion further above of the differences between the device of the '201 U.S. Patent to Chiuminatta et al. and the present invention, applies here as well.
U.S. Pat. No. 5,680,854 issued on Oct. 28, 1997 to Michael G. Kingsley et al., titled “Self Propelled Saw,” describes a relatively large and heavy duty saw having a symmetrical axle passing through the blade center, with the blade being driven from both ends of the axle shaft. The Abstract notes provision for vibration isolators with this configuration, but the vibration isolators only apply to the drive system; they do not do anything to dampen lateral vibration and flexing of the relatively large saw blade. In fact, no specific blade attachment is disclosed by Kingsley et al. The only components disclosed in the area of the blade hub, are the blade driveshaft and pulleys at each end thereof. It would appear that the blade as shown in broken lines is somewhat larger than could actually be accommodated by the mechanism, but in any event, no relatively large diameter collars for precluding blade vibration are disclosed by Kingsley et al.
U.S. Pat. No. 5,941,227 issued on Aug. 24, 1999 to Martin A. Bearden, titled “Portable Saw With Disconnectable Platform For Cutting Concrete For Controlling Cracks,” describes a relatively small, hand operated saw for cutting “green” concrete. The saw is detachably mounted on a roller platform for moving the saw smoothly over the concrete surface. Bearden is silent regarding any specific blade attachment means for his saw, only noting that the circular blade is attached to a shaft. No relatively large diameter collars for clamping the blade therebetween and eliminating lateral vibration of the blade, are disclosed by Bearden.
U.S. Pat. No. 6,112,736 issued on Sep. 5, 2000 to Martin A. Bearden, titled “Portable Saw With Improved Disconnectable Platform For Cutting Concrete For Controlling Cracks,” describes an apparatus closely related to that of the '227 U.S. Patent to the same patentee, discussed above. The same points raised in that discussion are seen to apply here as well.
International Patent Application No. WO 96/21,544 published on Jul. 18, 1996 to Diamant Boart, Inc., titled “Self Propelled Saw,” is based upon the same divisional application as the issued '854 U.S. Patent to Kingsley et al., discussed further above, with the assignee of the '854 U.S. Patent being the same entity as the applicant in the '544 International Application. The discussion further above of the differences between the saw of the '854 U.S. Patent and the present invention, is seen to apply here as well.
Finally, German Patent Publication No. 41 33 848 published on Apr. 15, 1993 to Artur Fischer describes (according to the drawings and English abstract) a masonry drill having a pair of stand-off spacers attached thereto. While the abstract states that the spacers serve to dampen vibration, such a drill bit and spacers are not analogous to the saw blade shaft and collars of the present invention. In any event, it is noted that the materials of the spacers of the '848 German Patent Publication are described as a “Kunststoffkappe” and “elastischen Kunststoff . . . Polyurethan,” i.e., a plastic cap and an elastomer polyurethane plastic, incolumn 2, respectively on lines 22-23 and 51 of the text. Such material is completely unsuitable for use in collars which clamp and compress a saw blade tightly therebetween to preclude lateral movement of the blade from the plane of rotation, as provided by the present collars.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a stabilizing collar for a concrete saw blade solving the aforementioned problems is desired.